How to make money with $1 slices

From the outside, Rosa's looks like any other dollar pizza store. Nothing remarkable, nothing to hint there's anything special about it except, as of a few weeks ago, a sign that reads "as seen on Ellen."

The story starts on Wall Street, where owner Mason Wartman, 27, was working when he decided his future success lay not in the hallowed halls of investment banks, but within the tomato-sauce-spattered walls of a pizza store.

"I always wanted to open my own business," he says. "I decided to come back to Philly and start a dollar pizza store because I saw the success and proliferation of dollar pizza stores in Manhattan."

So Wartman bid farewell to Wall Street and opened Rosa's, which he named after his mom. "My number one bit of advice if you're starting a business: Name it after your mom," he said. "It should have been 'Mary Gates Software Company'."

Wartman opened Rosa's in late 2013. One day a few months later, a customer asked if anyone ever came in short of money. Could he pre-purchase a slice for the next person who did? He referenced a similar approach in Italy where people can pre-purchase coffees for people who can't afford one.

Wartman took the money and reserved the slice. Intrigued by the Italian coffee tradition, he bought stacks of post-it notes and started telling customers, who pre-bought a slice and wrote a post-it to show the food was available.

The story eventually made its way to Ellen, who presented Wartman with the sign -- as well as a $10,000 check to go toward more free pizza. Wartman says business has doubled or even tripled since his appearance on the show, and Rosa's is now in the black.

For Michael Rodriguez, who's been homeless and unemployed since last year, the pizza is a high point of his day. "Pizza's my favorite, so it's a win-win and it's free."

The concept is a win for Rosa's bottom line as well. "We've given away 9,000 slices of pizza to homeless people -- that's $9,000 of business that wouldn't obviously otherwise have gotten sold," Wartman says.

Not only the advance sales, but the level of traffic generated by the novel concept is a necessity for a store like Rosa's that relies on high turnover to make a profit.

Wartman defines the approach as "an elegant solution" to the dual need for businesses to make money and for the hungry to eat. He's hopeful other businesses will adopt it as well.

"We have thousands of restaurants throughout the country. We could feed a lot of people very quickly if just a fraction of them acted in similar ways," he says, adding that the model would work best for quick-service restaurants like pizza stores or diners.

But pizza isn't the only thing bringing customers to Rosa's. Every post-it note displays words of hope, comfort or humor for those who may be having a hard time. Words, which Wartman points out, otherwise might not be said.

Rodriguez points out his favorite post-it: "I've been where you're at -- believe in God, do the right thing, trust me your miracle will come -- it just takes time."

It may not be a miracle, but Rodriguez recently started a new job and hopes to eventually move out of the shelter.

"Going through this, you get kind of depressed sometimes," he explains. "So you need some inspiring words -- and coming from someone you don't even know is even more inspiring."